com.bigdata.striterator.ChunkedArraysIterator Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Oct 24, 2007
*/
package com.bigdata.striterator;
import java.util.Arrays;
import java.util.NoSuchElementException;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* An iterator that visits the elements in the given iterator of arrays.
*
* @author Bryan Thompson
* @version $Id: ChunkedArrayIterator.java 2265 2009-10-26 12:51:06Z thompsonbry
* $
*/
public class ChunkedArraysIterator implements IChunkedOrderedIterator {
private boolean open = true;
/** buffer iterator. */
private ICloseableIterator bufferIt;
/** current buffer. */
private E[] buffer;
/** The order of the elements in the buffer or null iff not known. */
private final IKeyOrder keyOrder;
/**
* The index of the next entry in {@link #buffer} that will be returned by
* {@link #next()}.
*/
private int i = 0;
// /**
// * The element most recently returned by {@link #next()}.
// */
// private E current = null;
// /**
// * The #of elements that this iterator buffered.
// */
// public int getBufferCount() {
//
// return bufferCount;
//
// }
/**
* An iterator that visits the elements in the given iterator of arrays.
*
* @param a
* The iterator of arrays of elements.
*/
public ChunkedArraysIterator(final ICloseableIterator a) {
this(a, null);
}
/**
* An iterator that visits the elements in the given iterator of arrays.
*
* @param a
* The iterator of arrays of elements.
* @param keyOrder
* The order of the elements in the buffer or null
* iff not known.
*/
public ChunkedArraysIterator(final ICloseableIterator a,
final IKeyOrder keyOrder) {
if (a == null)
throw new IllegalArgumentException();
this.bufferIt = a;
this.keyOrder = keyOrder;
}
@Override
public boolean hasNext() {
if(!open) return false;
if (buffer == null) {
return bufferIt.hasNext();
}
// else {
//
// assert i <= buffer.length;
//
// if (i == buffer.length) {
//
// return false;
//
// }
//
// }
return true;
}
@Override
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
if (buffer == null) {
buffer = bufferIt.next();
}
E e = buffer[i++];
if (i == buffer.length) {
buffer = null;
i = 0;
}
return e;
// current = buffer[i++];
//
// return current;
}
/**
* @throws UnsupportedOperationException
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
// /**
// * Return the backing array.
// *
// * @see #getBufferCount()
// */
// public E[] array() {
//
// assertOpen();
//
// return buffer;
//
// }
/**
* Returns the remaining statements.
*
* @throws NoSuchElementException
* if {@link #hasNext()} returns false.
*/
@Override
@SuppressWarnings("unchecked")
public E[] nextChunk() {
if (!hasNext()) {
throw new NoSuchElementException();
}
final E[] ret;
if (buffer == null) {
/*
* We need to fetch the next buffer from the source iterator, and
* then we can just return it directly.
*/
buffer = bufferIt.next();
ret = buffer;
} else if (i == 0) {
/*
* Nothing has been returned to the caller by next() so we can just
* return the current buffer in this case.
*/
ret = buffer;
} else {
/*
* We have a buffer but we've already started return elements from
* it via next(), so we need to create a new buffer to return.
*/
final int remaining = buffer.length - i;
/*
* Dynamically instantiation an array of the same component type
* as the objects that we are visiting.
*/
ret = (E[]) java.lang.reflect.Array.newInstance(buffer.getClass()
.getComponentType(), remaining);
System.arraycopy(buffer, i, ret, 0, remaining);
}
// reset the current buffer
buffer = null;
i = 0;
return ret;
}
@Override
public IKeyOrder getKeyOrder() {
return keyOrder;
}
@Override
public E[] nextChunk(final IKeyOrder keyOrder) {
if (keyOrder == null)
throw new IllegalArgumentException();
final E[] chunk = nextChunk();
if (!keyOrder.equals(getKeyOrder())) {
// sort into the required order.
Arrays.sort(chunk, 0, chunk.length, keyOrder.getComparator());
}
return chunk;
}
/*
* Note: Do NOT eagerly close the iterator since the makes it impossible to
* implement {@link #remove()}.
*/
@Override
public void close() {
if (!open) {
// already closed.
return;
}
bufferIt.close();
open = false;
buffer = null;
i = 0;
}
// private final void assertOpen() {
//
// if (!open) {
//
// throw new IllegalStateException();
//
// }
//
// }
}
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